1. Field of the Invention
The present invention relates to a lens apparatus including an external force absorption structure.
2. Description of the Related Art
Optical apparatuses such as lens apparatuses require not only good optical performance but also durability against an external force due to impact or the like. Japanese Patent Laid-Open Nos. 10-293238 and 2006-64930 each disclose a lens apparatus including an external force absorption structure.
The lens apparatus disclosed in Japanese Patent Laid-Open No. 10-293238 has a configuration in which a holding member that holds a first lens unit and a ring member to which an optical member such as a filter is attached and that is disposed in a front portion of an outer circumferential part of the holding member sandwich an adjustment member and a biasing member. In such a configuration, an external force applied to the ring member moves the ring member rearward to a position where the ring member is brought in contact with the adjustment member while compressing the biasing member, and thereby the external force is absorbed.
Furthermore, the lens apparatus disclosed in Japanese Patent Laid-Open No. 2006-64930 has a configuration in which a front side lens barrel holding a lens and a rear side lens barrel into which the front side lens barrel is movably inserted are each provided with a taper surface, and in which a first lens barrel is biased in an optical axis direction by a biasing member, whereby the taper surfaces of the front and rear side lens barrels are brought in contact with each other. This configuration absorbs not only an external force applied in the optical axis direction but also an external force applied in a direction orthogonal to the optical axis is absorbed.
However, in the configuration of the lens apparatus disclosed in Japanese Patent Laid-Open No. 10-293238, since the ring member is moved rearward with respect to the first lens unit held by the holding member and thereby the lens apparatus (especially a wide-angle lens apparatus having a wide angle of view) may be increased in size in its radial direction. That is, in order to prevent the ring member moved rearward from interfering with the first lens unit, it is necessary to dispose the ring member apart from the first lens unit in the radial direction. In a lens apparatus having a wide angle of view, since light rays having a large angle with respect to the optical axis enter a peripheral portion thereof, it is necessary to increase a diameter of the ring member in order to prevent vignetting of the light rays due to the ring member. As a result, the lens apparatus is increased in size in the radial direction.
Moreover, in the lens apparatus disclosed in Japanese Patent Laid-Open No. 2006-64930, positioning of the front side lens barrel holding the lens unit in the optical axis direction and in the direction orthogonal to the optical axis with respect to the rear side lens barrel is performed by the contact of the taper surfaces of the front and rear side lens barrels, which may decrease positioning accuracy.